1. Field of the Invention
This invention relates to endless coated abrasive articles, in particular, coated abrasive belts having a splice made by means of radiation curable adhesives.
2. Discussion of the Art
The conventional method for making an endless coated abrasive article, i.e., a belt, involves the steps of cutting a coated abrasive sheet to the desired length, applying a splice adhesive over both cut ends of the side of the coated abrasive sheet not bearing abrasive, allowing the coated abrasive sheet to stand for a sufficient time to allow the solvent to flash off from the adhesive, abutting the two cut ends of the coated abrasive sheet to form a joint, applying a splice medium over the joint, and solidifying the splice adhesive. The splice adhesive is typically solidified by heat and pressure.
Polyurethane splice adhesives, which are in common use, are partially cured by heat and then are fully cured over time at room temperature to effect solidification. However, cure time can take up to several days, thereby requiring the coated abrasive belt to be handled with care.
The time required for the solvent to flash off can range anywhere from five to 60 minutes, thereby creating a bottleneck in the manufacturing process. Furthermore, removal of the solvent gives rise to environmental concerns.
Polyurethane adhesives are described in U.S. Pat. No. 4,082,521 (McGarvey), which discloses a splice adhesive selected from the group consisting of polyurethane, epoxy, nylon-epoxy, and nylon-phenolic adhesives; U.S. Pat. No. 3,154,897 (Howard), which discloses a splice adhesive selected from the group consisting of polyurethanes, bisamide, polyesters, epoxy polyesters, epoxy polyamides, bis-ketones, diacrylates, styrene-polyesters, and the like; and U.S. Pat. No. 4,194,618 (Malloy), which discloses a urethane-based splice adhesive film that does not have a solvent associated with it. However, the process described in this patent is complex and requires a lengthy period of drying.
There are two major types of splices for endless coated abrasive sheets, the butt splice and the lap splice. In the butt splice, two ends of the coated abrasive sheet abut. The ends are held together by a splice adhesive, with a splice medium overlying the splice adhesive and the two ends. A splice medium can be a reinforced polymeric film, a woven fabric, or the like. In the lap splice, one end of the coated abrasive sheet overlaps the other end, such that the abrasive bearing side of one is in contact with the side of the other not bearing abrasive. The ends are held together by a splice adhesive alone; generally, there is no splice medium as in a butt splice.